London cyclists who unwittingly chain their bikes up in the wrong place could soon be in for a nasty surprise.

Campaigners fear that if Ken Livingstone's transport agency Transport for London and London's 33 councils get their way, bikes chained to lamp-posts or railings outside designated cycle parking areas will become fair game for forcible removal by council officers.

TfL and the boroughs are jointly lobbying for new powers in a private bill that gets its first reading in the House of Lords today. Should the new laws be approved, councils will for the first time be legally empowered to seize cycles without warning.

The implications of the bill are a potential embarrassment for the mayor, who is a strong advocate of cycling and is aiming for an 80% increase in cycling by 2010 compared to 2000 levels. "Bike owners may go to work and have no bike when they are going home," says Tom Bogdanowicz, campaigns officer at the London Cycle Campaign. "This legislation will undermine any plans the mayor has to increase cycling."

More worrying is the potential long-term impact the new laws may have on Livingstone's ambitions for making London a world leader in sustainability. "The environmental implications of this are obvious," says Bogdanowicz. "The mayor not only needs more cycling to reduce congestion, but also to cut pollution and improve the health of Londoners, for which he has a responsibility."

The bill also appears to contradict several recent environmental initiatives promoted by the mayor. A Low Emission Zone for central London is set to come into force on February 4, while the London Green Homes Initiative went live on December 4, offering a central information source on the reduction of domestic emissions. Last year Livingstone also announced a detailed plan to switch a quarter of the capital's power supply to local combined heat-and-power systems by 2025, and to cut London's carbon emissions by 60% within 20 years.

Even though it is jointly promoting the bill, TfL is quick to deflect any blame away from itself and on to London Councils, the umbrella body for the capital's boroughs that has been involved in preparing the draft legislation.

London Councils argues that the objective of the bill is not to remove bicycles, but other health and safety hazards such as advertising boards and building materials left on walking routes. "This bill is not about decluttering, it's about safety," says the body's director of transport Nick Lester. "Anything councils want to take action on has to be causing serious obstructional damage."

However, Lester concedes that this could mean bicycles. "If a bike was parked in a selfish way so that it obstructed a footway, it could come within the ambit of this bill – and I don't think that's unreasonable," he says.

Lester maintains that the proposed laws would be unlikely to affect most bikes chained to railings and causing no obstruction. Nonetheless, the bill has caused enough of a stir for London assembly Green party member Darren Johnson to raise the issue in a written question to the mayor last week.

"This heavy-handed attempt has been tried in the past but the clause was removed," Johnson says. "We hope this ridiculous idea will also be strangled in its early stages.

"If implemented, it would have a really negative effect; if more and more people are cycling in London, they need somewhere to put their bikes safely. Taking these places away isn't going to encourage more people to cycle."

In his question to Livingstone, Johnson says he asked the mayor to put pressure on the bill's promoters to ensure bicycles are explicitly exempted from the proposed laws. "It would fly in the face of his strategy to promote cycling if he didn't throw his weight behind this," Johnson says.

Being a private bill, the public can petition either house of parliament on amending its contents, and the LCC is planning to do this as the draft passes through its Lords stage.

"There is no question that a large proportion of people in this town want to cycle," says Bogdanowicz. "If the mayor removed the barriers to cycling a lot more people would do it and London would be a cleaner and healthier place. To support legislation that undermines this objective is absolutely contradictory."